The present invention relates to the use of a composition comprising an oil with a high content of essential fatty acids of xcfx893 and xcfx896 type, preferably blackcurrant seed oil, and at least one compound selected from xcex2-carotene, lycopene, tocopherol and its derivatives, tocotrienols and their derivatives, ascorbic acid and nicotinamide as a nutritional supplement intended for preventing and/or combating the harmful effects of xenobiotics on the skin, in particular on the skin""s immune system.
The skin is continually in contact with xenobiotics, which are substances that are referred to as being foreign to the cell""s natural metabolic pathways, such as medicinal products, pesticides, pollutants, tobacco or UV. The skin suffers daily attack when it is exposed to these agents, in particular to UV rays which cause immediate damage to the skin, such as sunburn, photosensitivity or immunosuppression reactions, but also long-term effects such as photo-ageing or skin tumours.
Most of these adverse effects are associated with the production of oxygenated free radicals. They have the property of depolymerizing certain skin constituents such as collagen or elastin, or else of degrading membrane lipids or DNA, which results in the production of endobiotics that are harmful to the skin, such as toxic metabolites or inflammation mediators which finally lead to a loss of integrity of the cell membranes. The action of xenobiotics and endobiotics is particularly important as regards the skin""s immune defences. Specifically, a depletion of the Langerhans cells can result in a penetration of pathogens into the body without the general immune system being alerted. This results, for example, in a higher propensity for the appearance of infections via pathogens.
The use of compounds capable of inhibiting or neutralizing the action of xenobiotics and endobiotics, in particular oxygenated free radicals, might make it possible to reduce the skin damage induced.
Among these compounds, vitamins and essential fatty acids have, in a certain number of in vitro and in vivo studies, shown protective activity with respect to harmful xenobiotics and endobiotics.
xcex1-Tocopherol has shown that it can prevent the oxidation of polyunsaturated fatty acids, which are essential components of cell membranes and are particularly sensitive to damage induced by free radicals (1). This compound also has anti-inflammatory activity by means of direct action on the enzymatic systems of the arachidonic cascade (2). Other components belonging to the tocotrienol family (xcex1-, xcex3-tocotrienols and their derivatives) have shown noteworthy action in preventing cell damage associated with an exposure of the skin and the superficial body growths to free radicals and UV rays (3) and to ozone (4). In addition, it has been demonstrated that the role of tocopherols and tocotrienols is important as regards the activation of the immune system (5).
Ascorbic acid can also trap the oxygenated free radicals (more particularly singlet oxygen) involved in many oxidative processes which damage cells (6). In addition, xcex1-tocopherol combined with ascorbic acid shows effects on increasing the Minimum Erythemal Dose (7).
xcex2-Carotene is a vitamin A precursor which acts as a chemical screening agent (with an absorption maximum in the UVA and visible range) and protects against lipid peroxidation (8, 9). It is often used to prevent photodermatoses (10). In general, carotenoids (xcex2-carotene, lycopene, lutein, zeaxanthin and astaxanthin) are also involved in modulating the immune system (WO 98/44808). Lycopene is also a free-radical trap (11) and nicotinamide is often used in the same way as a xcex2-carotene against photodermatoses (12).
Blackcurrant seed oil, which contains essential fatty acids of (xcfx893 and xcfx896 type, has shown a certain level of efficacy in reducing certain inflammatory processes (13).
In the context of the present invention, it has been found, surprisingly, that a combination between blackcurrant seed oil and the abovementioned compounds has, in a nutritional composition, an advantageous effect for reducing the harmful action of both xenobiotics and endobiotics of the free-radical type or of the type generating free radicals, in particular by reinforcing the skin""s immune defences. After repeated daily administration, such a composition affords protection to the Langerhans cells.
Thus, the present invention relates to the use of a composition comprising an oil with a high content of essential fatty acids of the type xcfx893 and xcfx896 and at least one compound selected from xcex2-carotene, lycopene, tocopherol and its derivatives, tocotrienols and their derivatives, ascorbic acid and its derivatives, nicotinamide and a trace element, as a nutritional supplement intended for reinforcing the immune defences of the skin and the superficial body growths.
More specifically, this nutritional supplement may be intended for preventing and/or combating the harmful effects of xenobiotics on the skin, in particular on the skin""s immune system, in particular for reducing the cytotoxic effects of xenobiotics on the Langerhans cells. In this sense, the composition according to the invention is useful for combating or preventing photodermatoses, for improving the skin""s tolerance to sunlight and for preventing ageing of the skin and the superficial body growths and their disequilibrium due to free radicals.
In one advantageous embodiment, the composition comprises blackcurrant seed oil, since this oil is rich in essential fatty acids of xcfx893 and xcfx896 type, in particular xcex1-linoleic acid, xcex1-linolenic acid and xcex3-linolenic acid.
This oil comprises:
Essentially, the xcfx893 fatty acids have a beneficial effect on erythema induced by UVB and are useful in the prevention of photocarcinogenesis. The xcfx896 fatty acids are particularly important in the context of the invention since they participate in keratinization.
Needless to say, an oil equivalent to blackcurrant seed oil in terms of the abovementioned essential fatty acid composition can be used in the dietary supplement described according to the invention.
In one preferred aspect of the invention, the composition comprises blackcurrant seed oil, xcex2-carotene, lycopene, tocopherol or its derivatives, tocotrienols or their derivatives, ascorbic acid or its derivatives, and nicotinamide.
The composition can also comprise a trace element, preferably selenium in any form, in particular in the form of selenium-containing yeasts.
Selenium is a co-factor which increases the activity of glutathione peroxidase (GPX), protects cells against the harmful effects of organic and inorganic peroxides, and stabilizes membranes by becoming incorporated into the disulphide bridges, thus leading to a decrease in the amount of arachidonic acid released during the inflammatory response. Thus, this compound is also useful as a compound for protecting the skin against xenobiotics.
The composition advantageously comprises at least 25% by weight, preferably about 50%, of blackcurrant seed oil. It can also comprise:
at least 5% by weight, preferably 15 to 18%, of ascorbic acid;
at least 4% by weight, preferably about 8%, of lycopene;
at least 5% by weight, preferably about 10%, of selenium;
at least 2% by weight, preferably about 4%, of xcex2-carotene;
at least 1% by weight, preferably about 3%, of nicotinamide;
and/or at least 1% by weight, preferably about 2%, of tocopherol or its derivatives, in particular tocopheryl acetate.
A composition according to the invention may thus comprise approximately, by weight:
53% blackcurrant seed oil,
4% xcex2-carotene,
8% lycopene,
2.2% tocopheryl acetate,
15 to 18% ascorbic acid, and
3% nicotinamide;
and optionally about 10% by weight of selenium.
Among the excipients which are added, those preferably selected are yellow beeswax, soybean lecithin, glycerol, liquid paraffin and gelatin, preferably of marine nature.
Needless to say, it is possible to add to the composition any other active compound known in the prior art. Mention may be made, for example, of nucleic acids or nucleotides, amino acids, in particular lysine and arginine, peptides, sugars, in particular biologically active sugars, retinoids, plant extracts, in particular from green tea or from soybean, any extracts from plants rich in isoflavones, DHEA and melatonin.
The composition according to the invention can be in the form of gel capsules, soft capsules, sugar-coated or plain tablets, including delayed forms, suitable for oral administration. Thus, the invention relates to a composition as defined above.